Optimal Biodegradable Scaffolds and Progenitor Cells for Effective Bone Regenerat

描述（由申请人提供）：骨修复和再生代表着一个不断扩大的，数十亿美元的市场，通过口腔/颌面外科和矫形外科领域解决。常见的病例包括由于创伤、肿瘤切除、翻修手术、发育畸形和不愈合骨折造成的骨质流失，以及由于牙齿缺失和牙周病造成的牙齿骨质流失。目前可用的治疗方案（即自体移植物、同种异体移植物等）远非理想，往往导致有限程度的结构和功能恢复，以及其他严重的并发症。骨组织工程（BTE）可能是一种更好的替代治疗方法。成功的BTE关键取决于有效的三维、可生物降解的支架和充足的血管供应。本研究的总体目标是开发一种优化的可生物降解支架，植入临床相关细胞以促进骨再生和血管化。本研究的重点是聚（85乳酸-co-15乙醇酸）（PLGA）微球支架，因为它们具有可生物降解、骨相容性和与人骨的机械相容性。不幸的是，由于无法支持足够的氧气和营养物质的质量运输以及新生血管的形成，这些微球支架（孔径约100 5m）实现的骨再生仅限于支架表面。非plga微球支架具有更大的孔径（即> - 400 - 5m），虽然与人类骨再生不具有机械兼容性，但已被证明可以缓解这些限制，改善细胞浸润，并最终增加整个支架的骨形成和血管化。此外，最近的研究表明，通过共同培养两种临床相关的细胞群，外周血来源的内皮祖细胞（EPCs）和骨髓来源的间充质干细胞（MSCs），体外预血管化支架可以促进体内骨形成和血管化。我们假设，预血管化的、机械强度高的PLGA微球支架具有较大的孔径（即中等大小的孔隙），通过改善整个支架的细胞增殖、矿化和血管化，将促进骨形成的增加。我们建议通过三步走的过程来实现这个主要目标。首先，我们将设计，制造和表征（即孔隙率，连通性和机械强度）新颖的中等多孔性和机械强度的PLGA微球支架。其次，我们将评估这些中等多孔PLGA微球支架与两种临床相关细胞群相比，在体外证明矿化增强和原始血管网络形成的能力。最后，我们将通过兔尺骨缺损模型研究预血管化的中等多孔PLGA微球支架在体内增强的骨再生能力。我们的方法旨在通过开发一种能够实现全功能和结构骨再生的技术，显著推进基于支架的BTE的最新技术。

DESCRIPTION (provided by applicant): Bone repair and regeneration represents an expanding, multi-billion dollar market addressed through the fields of oral/maxillofacial and orthopaedic surgery. Common cases involve bone loss due to trauma, tumor resection, revision surgery, developmental deformities and non-union fractures, and dental bone loss as a result of missing teeth and periodontal disease. Currently available treatment options (i.e., autografts, allografts, etc.) are far from ideal, often resulting in a limited degree of structural and functional recovery, as well as other serious complications. Bone tissue engineering (BTE) may serve as a superior alternative treatment. Successful BTE critically depends on an effective three-dimensional, biodegradable scaffold, and an adequate vascular supply. The overall objective of this study is to develop an optimized biodegradable scaffold, seeded with clinically relevant cells to promote enhanced bone regeneration and vascularization. This study focuses on poly(85 lactide-co-15 glycolide) (PLGA) microsphere scaffolds since they are biodegradable, osteocompatible, and mechanically compatible with human bone. Unfortunately, bone regeneration achieved with these microsphere scaffolds (pore size ~100 5m) is limited to the scaffold surfaces, due to failure to support sufficient mass transport of oxygen and nutrients, and neo-vascularization. Non-PLGA microsphere scaffolds with larger pore sizes (i.e., > 400 5m), although not mechanically compatible with human bone regeneration, have been shown to ease these limitations, improve cell infiltration, and ultimately, allow for increased bone formation and vascularization throughout the entire scaffold. In addition, recent work has demonstrated that pre-vascularizing scaffolds in vitro by co-culturing two clinically relevant cell populations, peripheral blood derived - endothelial progenitor cells (EPCs) and bone marrow derived - mesenchymal stem cells (MSCs), enhances both bone formation and vascularization in vivo. We hypothesize that pre-vascularized, mechanically strong PLGA microsphere scaffolds with increased pore size (i.e., moderately-sized pores) will promote increased bone formation, by improving cell proliferation, mineralization and vascularization throughout the entire scaffold. We propose to achieve this main objective through a three- step process. First, we will design, fabricate and characterize (i.e., porosity, interconnectivity and mechanical strength) novel moderately-porous and mechanically strong PLGA microsphere scaffolds. Second, we will assess the ability of these moderately-porous PLGA microsphere scaffolds seeded with two clinically-relevant cell populations to demonstrate enhanced mineralization and the formation of primitive vascular networks compared to control scaffolds in vitro. Lastly, we will study the enhanced bone regeneration ability of our pre- vascularized moderately-porous PLGA microsphere scaffolds in vivo via a rabbit ulnar bone defect model. Our approach is designed to significantly advance the state-of-the-art in scaffold-based BTE through the development of a technique to enable fully functional and structural bone regeneration.